1. Field of the Invention
The present invention relates generally to a system for accessing a post office system with a remote computer using downloaded applets and, more specifically, to a system for selectively downloading messages from the post office system.
2. Description of the Related Art
An electronic post office system maintained within a network file server allows multiple computer users linked to the network file server to transmit electronic messages to each other. A message is the basic unit of exchange in the post office system. A message can include file attachments such as text, graphics, sounds, binary files, electronic forms, fax pages or any other data objects. The post office is the central repository for all messages and is typically implemented in a database system in the network file server. The post office has a mail directory, which lists all the people, post offices and gateways for message exchange. Each user maintains an individual mailbox within the post office system, which might include an inbox of incoming messages, drafts of text messages not yet sent, an outbox of sent messages, trash folders of deleted messages, etc. Each user in the post office system has an assigned name which is used to identify and route mail to the user.
FIG. 1 illustrates how client computers 2a, 2b access a post office system 4 within a server computer 6 via a network connection 8 (e.g., LAN, WAN, etc.). FIG. 2 illustrates how a computer 10 at a remote location can connect to a post office system 20 via a TCP/IP connection 12 and the Internet 14. The post office system 20 is included in a server 16 which runs the POP3 protocol 18. A protocol is used to regulate communication between the client computer and the post office system. Protocols which regulate the flow of messages to a post office system via the Internet include the Post Office Protocol version 3 (POP3), as shown in FIG. 2, the Internet Message Access Protocol version 4 (IMAP4), Lightweight Directory Access Protocol (LDAP), etc. Both the client and post office system must use compatible protocols. For instance, software programs such as Netscape Navigator, Eudora Pro, and Microsoft Internet Explorer include the POP3 protocol, thereby allowing a client computer running these programs to access a post office system compatible with POP3.
In prior art systems, the client computer must include software using a mail protocol compatible with the protocol for the post office system. Thus, if a client computer has software running the POP3 protocol, but not IMAP4, then such client computer will not be able to access a post office server only compatible with IMAP4. Prior art systems thus require users to make sure that they have installed software including a protocol compatible with the protocol used in the post office system they want to access before they attempt to access the post office system.
The IMAP4 protocol provides "online" manipulation of messages in the mail server and leaves the messages on the server. With IMAP4, users can remotely access the post office system, draft messages, view messages, and manage and manipulate post office files and folders locally within the server. The POP3 protocol and other similar proprietary protocols, on the other hand, provide "offline" manipulation of messages. With POP3, the remote client computer downloads and deletes all the messages from the post office system. In POP3, all message processing is local to the client computer.
Although, presently, the POP3 protocol is more widely used than IMAP4, IMAP4 is a more efficient protocol because IMAP4 minimizes data transfer time. With IMAP4, the remote client computer may review messages stored in the post office system and selectively download only desired messages. In this way, data transfer is limited to only those messages the user wants to download. On the other hand, with the POP3 protocol, the remote client computer must download all messages, even those the user has no interest in downloading. Thus, POP3 maximizes data transfer time and needlessly consumes client computer system resources.